SingleCall

SingleCall is a term used in Microsoft .NET Remoting to describe a well-known object activation mode. In SingleCall mode, the runtime creates a new server-side object instance to handle each method invocation from a client, and the instance is released immediately after the call completes. As a result, server-side state is not preserved between calls, making the service effectively stateless.

When a remote object is registered with the SingleCall mode, multiple concurrent calls may be serviced by different object instances in parallel. This can simplify thread safety for the service implementation, but it also introduces the overhead of frequent object creation and destruction.

SingleCall contrasts with the Singleton activation mode, where a single server-side instance handles all incoming calls for the lifetime of the application. There is also Client-Activated activation, where a client creates an instance that lives on both sides for a period of time.

Configuration typically involves specifying the activation mode when registering the well-known service type, indicating WellKnownObjectMode.SingleCall. The mode mirrors the intended design of stateless services where no client-specific state is retained on the server between calls.

Limitations: SingleCall is best suited for stateless operations. For operations requiring client-specific or long-lived state, other activation modes are more appropriate. In modern Microsoft stacks, .NET Remoting and its SingleCall mode are considered legacy, with WCF and newer technologies recommended for distributed communication in current frameworks.